Production of ascorbic acid esters



3,132,154 PRODUCTION OF ASCORBIC ACID ESTERS Hans Meyer-Boring, Cranaehstrasse 49, Hamburg- Gross-Flottbek, Germany No Drawing. Filed Jan. 9, 1958, Ser. No. 707,858 Claims priority, application Germany Dec. 7, 1953 16 Claims. (Cl. 260-34337) The present invention relates to a process for the preparation of a water soluble therapeutic compound-which can exert an antibacterial effect. This eifect is bactericidal or bacteriostatic according to the concentrations or conditions -of use and. no harmful secondary efiects are produced'in the body. The present invention relates further on to new water soluble therapeutic compounds with im- It is known to stabilize ascorbic acid by it with amino acids, such as cystine, cysteine or :glutathione, or vice versa to stabilize amino acids with ascorbic acid. Those stabilized products are mere mixtures with less therapeutic value which only can be compensated by I the use of larger doses.

t I have found a new process for preparing water'soluble antibacterial compounds having improved bacterio static or bactericidal effects which cannot be achieved by the former known mixtures or simple salts of the com- ..ponents. Furthermore, I have found new compounds having a better stability in the body, and being not sub jected to such a rapid and strong catabolism in the body as ascorbic acid alone. Their increased stability enables these products to. exert their effect at the place where they are used by the body for preventing injuries or for combating illness. As a particular advantage, however,

itis to be emphasized that the useof my new antibacterialcompounds do not engender any injurious secondary eftects, such as, for example, harm to the blood, damage to the intestinalfiora, allergic phenomena or dermatitis.

lit is'astonishing that a small amount, for example, Q.03- 1.0 mg. per mouse, of my new compounds would be sufficient,-as proved by experiments with animals, to produce therapeutic effects which are substantially equal or even far superior to those of known bactericidal agents, such, tor example, as sulphonamides or antibiotics. This is due to a decided, potentizing effect, which-cannot be achieved by simultaneous-or successive doses of the components alone orby mere mixtures. t i

According to the process of my invention, the anti bacterial, compounds are obtained by reacting ascorbic.

acid with naturally occurring amino acids. in the following the term ascoubic acid covers also the following compounds as listed in Table I TABLE I The term naturally occurring amino acids covers such with or without a SH- group or a S-CH those amino acids could be used as such or in the form r 3,132,154 Ce Patented May 5, 1 54 of their salts or their acid Table 11:

TABLE LI Glycine, alanine, leucine, isoleucine, tyrosine,

cystine glutamic acid;

Cysteine, homocysteine, glutathione;

Methionine, ethionine;

Mixtures of the above-mentioned substances.

According to the invention the ascorbic compounds as listed in Table I are reacted in liquid medium with the amino compounds as listed in Table II which are in dispersion or solution. The reactionproduct is separated from the reaction mixture, audit necessary purified by crystallization; To ensure a rapid and complete reaction and to form highly effiective products, the reaction preferably is carried out at elevated temperatures, for example at temperatures between and 130 C., more especially between and 80 C. The generally water expedient to maintain them Within the molar ratios 2:1

and 1:2 inclusively.

I When having a molar ratio between the two-reacting components of 1:1, the reaction according tomy invention could be symbolized by the following formulae:

3 in which R is a residue of a naturally occuring amino action.

acid withoutthe COOH group as listed in Table II; C

and C are the second and the third carbon atoms of an endiol containing ascorbic compound, respectively;

When the molar ratio 2:1 (amino compoundzascorbic compound) is used the enol-linkage between the two amino. compounds and the one ascorbic compound will take place at both carbon atoms-ofthe latter, namely at the second and third carbon of the ascorbic compound.

When the molar ratio 1:2 (amino compoundzascorbic compound) is used there will be only one enol linkage between the acid group of the amino compound and the third carbon atom of one mol of the It is assumed that the other mol of the ascorbic compound is coupled with the amino group of the amino acid by a probably complex linkage. 1

The reaction according to my invention can be pro moted by carrying out the reaction in the presence of sub stances which promote esterification, such as acids. Advantageously hydrochloric acid could beused.

I found that adding of thionyl chloride or boron 'trifluoride will promote the esterification reaction. In this case it is assumed that the enol linkage occurs by reaction of the chlorine atom of a previously or intermediately formed acid chloride of the naturally occurring amino acid; said chlorine atom reacts with the hydrogen atom of the enolic OH-group of the ascorbic compound, .or the sodium atom, for instance, when sodium ascorbate is used. Here, the presence of a dehalogenating agent such as sodium carbonate or pyridine will give a smoother re chlorides and are listed in ascorbic compound.

7 tion:

My new antibacterial compounds, therefore, when a 1 :1 molar ratio (amino compoundzascorbic compound) is used have the following formula:

. I 1. g The following examples are illustrative of my inven Example 1 i r 3.52 partsof anhydrous ascorbic acid and 3.15 parts of anhydrous cysteine hydrochloride are dissolved with heating in a nitrogen atmosphere in 40 parts of absolute alco hol. After cooling to room temperature, 0.2 part of freshly distilled thionyl chloride is added. The mixture is then left to stand for 24, hours. It is concentrated under reduced pressure down to a volume of about parts and thereafter precipitated with 250 parts of dried ether. The

precipitate is oily first r of all, but solidifies after a timeinto a white crystalline mass. The precipitate is filtered with suction and dried. The'yield is practically quantitw tive.

Example. 2

3.52 parts of anhydrous ascorbic acid and 3.15 parts'of anhydrous cysteine hydrochloride are dissolved with heat:

' ing in 40 parts of absolute alcohol. After cooling, about 0.3 part of'boron trifluoride is introduced; The further treatment is carried out as indicated in Example 1.

Example 3 25 parts of acetone are poured on to 1 part of anhydrous cysteine hydrochloride and 8 parts of anhydrous ascorbic acid in a nitrogen atmosphere and 0.1 part of thionyl chloride is added. The }mixture is then left to stand for 48hours in the dark at room temperature. It is filtered oil with suction, the precipitate is washed with a little acetone and the filtrate precipitated with 150 parts of absolute ether. After 24 hours,- the precipitatehas be come crystalline; The solvent is filtered oif with suction and the precipitate washed with a little ether.

Example 4 I 6-8 cc. (0.050.06 mol) of ultra-pure freshlydistilled thionyl chloride are added dropwise' at 20 C. in the course of 10 minutes to 3.1 g. (0.02 mol) fine ly' powdered (mesh 1600) anhydrous cysteine hydrochloride. The mixture is then heated in a water bath to 37 C. The evolution of gas which takes place is terminated after 25-30 minutes. In order to complete the reaction, the

mixture is shaken for 3 to 4' hours and the product whichis obtained is washed with'dry petroleum ether. The residues of petroleum ether are removed in'vacuo of 1215 torr and at a temperature of 16 C.

1.9 g. (0.01 mol) of the cysteine acid chloride hydro.- chloride obtained in this manner are-mixed at a tempera ture of 404S C. with 2.0 g. (0.01 mol) of sodium ascorbate, which has previously been finely, suspended in 250 parts 'of absolute alcohol. Hereby sodium chloride is precipitated and the remaining solution becomes clear. Themixture is thenkept for one night under an inert gas, for

example nitrogen, the solution is then separated from the precipitated sodium chloride by decanting, and the alcohol is distilled oil in vacuo ata temperaturerof 42 C. and

under a nitrogen atmosphere of 25 torr. As the solution commences to become cloudy, precipitation is carried out with dry ether and the separated precipitation product is recrystallizedfrom absolute alcohol.

A yield of about 2.2 g. colourless water soluble crystals is obtained having not a quite exact melting point and a molecular formula of C H O NSHCI.

The crystallographic test proves that the obtained rhombic crystals are of uniform character. Analytic investigation shows that the reaction product has still the double linkage because a positiveiron ferrichloride reaction is obtainable; also the SH group remains unchanged in the reaction product which was proved by a positive sodium nitro prusside reaction. The coupling of cysteine I takes place at the C or C atom which-is proved by potentiometric'titration and by a well defined maximum at 360 mu.

' Example 5 C H O N S ZHCI j I Example 6 V a The reaction can also be carried out by reacting 1 mol of cysteine 1 acid chloride hydrochloride obtained according to Example 4 with 1 mol sodium ascorbate and a further mol ascorbic acid; this is accomplished in the following manner:

- larger than the eifect obtained with a mere mixture of a suspension of 1.98 g. of sodium ascorbate in 100 cc. of

A suspension of 0.01 mol or 1.9" g. of cysteine acid chloride hydrochloride in 50 cc. of petroleum ether (boiling point 50 C.) are mixed with 0.01 mo1=1.76 g. ascorbic acid and with 0.01 mol=2.0 g. sodium ascorbate. Themixture is stirred under nitrogen atmosphere or by passing nitrogen through the reaction mixture for 4 hours at room temperature; simultaneously a slight vacuum is maintained. The'siolvent is then distilled off, ultimately at reduced pressure, then'in vacuo. It is not necessary to separate the formed. sodium, chloride when the obtained product is used for ther apeutical purposes. The strong bactericidal efiect'of the reaction product is considerably those components; this also is an evidence for the reaction.

Example 7 I The hydrochloride of methionine acid chloride is prepared from methionine and phosphorus pentachloride in carbon tetrachloride by the process described by S. Levine in I. Am. Chem. Soc.,176, 1382(1954).

1.92 g. of this strongly hygroscopic compound are suspended with exclusion of moisture in .100 cc. of dry ether,

ether is added and the further process is carried out as described in Examples 1 and 2. After purification, there are obtained water soluble colourless prisms, the sulfur content of which is 9.1% and the nitrogen content 4.2%, which corresponds to an empirical molecular formula of CmHwOqNSl'IClp 1 I Example 8v Alanine acidchloride by hydrochloride is prepared according to the method described in Example 7. 1.44 g. of said acid chloride are suspended withexclusion of moisture-in cc. of dry ether, a suspension of 1.76 g. ascorbic acid in 100 cc. of ether is added (whereby the ascorbic acid is partially dissolved in ether). Thereafter 1.06 g. finely powdered anhydrous sodium carbonate are .added. After displacing the air contained in the vessel and can be purified according tothe method described in Example 4.. The ethyl alcohol used for the extraction should have a pH-value of 6.0-6.5, whichis obtained by.

adding alcoholic hydrochloric acid dropwise. The product obtained is water soluble and colourless, the yield of 2.0 g. liasia'molecularformula" of C H O N.HCl and an expected nitrogen content of 4.9%.

U Example 9 The same method as in Example 8 is used, but 0.79 g. pyridine are added instead of sodium carbonate. The formed pyridine hydrochloride is removed by washing with methyl alcohol at room temperature. The reaction product is the same as the one in Example 8.

Also acid chlorides of cystine, leucine, tyrosine, acetyl methionine, ethionine could be used as reactants with ascorbic acid, sodium ascorbate, monomethyl ascorbic acid or other ascorbic compounds as listed in Table I. The special conditions of the reaction correspond to those of the above mentioned examples and could be changed within certain limits by a person skilled in the art.

Relatively large series of comparative tests on animals were carried out with the products prepared according to my invention. Highly virulent cultures were employed for these tests with mice having an average weight of 10-15 g.; the cultures were used in an amount being times stronger than the minimal lethal dose and being in the form in which they originate from human beings, after they had passed through five animals to increase their virulence. The following cultures were used:

Pneumococcus, Streptococcus haemolyticus, Staphylococcus pyogenes (haemolyticus) and Bacterium coli haemolyticum. In some cases Staphylococcus, Oxford strain, and Streptococcus haemolyticus Aronson were used. Mice (controls animals andtest animals) were intraperitoneally infected with these bacteria, with three platinum-wire loops in each case. After dilferent time intervals (up to 4 /2 hours after infection) the test animals received a single dose of the treatment medium in increasing amounts according to the time interval. The untreated control animals died, whereas the test animals treated with the products according to my invention in the amount of 0.040.3 mg. per mouse lived. In comparison, the same effect is obtained by using sulphona- 3 mides in the amount of 12 mg. per mouse, and 0.020.2 mg. per mouse by using anti-biotics, such as teramycin or aureomycin. a

The mere mixture of the components, for instance cysteine hydrochloride andascorbic acid or sodium ascorbinate in a physiological sodium chloride solution are without any bactericidal effect. The animals treated with those mixtures died in the same way as the untreated control animals; only some dubious effects were obtained when increasing the amount 200-500 times.

While the invention has been described, it is not intended to be limited to the details given, since various modifications or changes may be made without departing in any way from the spirit of my invention. This application is a continuation-in-part of application Serial No. 471,908, filed November 29, 1954, now abandoned.

What I claim as new and desired to be secured by Letters Patent is:

1. A process for the preparation of an ester 'of an amino acid selected from the group consisting of glycine, alanine, leucine, isoleucine, tyrosine, cystine, glutaminic acid, cysteine, homocysteine, gluthathione, methionine and ethionine with ascorbic acid which comprises heating under exclusion of oxygen an endiol compound selected from the group consisting of ascorbic acid, its alkali metal salts and its alkaline earth metal salts with a compound selected from the group consisting of glycine, alanine, leucine, isoleucine, tyrosine, cystine, glutaminic acid, cysteine, homocysteine, gluthathione, methionine, ethionine lute alcohol, acetone, ethyl ether and petroleum ether at a temperature between 30 and 130 C. in the presence of a catalyst selected from the group consisting of hydrochloric acid, thionyl chloride and boron trifluoride and recovering the reaction product .from the reaction mixture in solid form.

2. A process for the preparation of an ester of an amino acid selected from the group consisting of glycine, alanine, leucine, isoleucine, tyrosine, cystine, glutaminic acid, cysteine, homocysteine, glutathione, methionine and ethionine with ascorbic acid which comprises heating under exclusion of oxygen ascorbic acid with an acid chloride of a naturally occurring amino acid selected from the group consisting of glycine, alanine, leucine, isoleucine, tyrosine, cystine, glutaminic acid, cysteine, homocysteine, glutathione, methionine, ethionine and their hydrochlorides in a waterfree and indifferent liquid medium selected from the group consisting of absolute alcohol, acetone, ethyl ether and petroleum ether, at a temperature between '30 and 130 C. in the presence of an alkaline compound selected from the group consisting of silver carbonate, sodium carbonate and pyridine and recovering the reaction product from the reaction mixture in solid form. t

3. The process of claim 2 in which the ratio of the endiol compound and the second compound reacted is from 2:1 to 1:2.

4. The process of claim 2 in which the reaction is carried out in a dry nitrogen atmosphere.

5. A process for the preparation of an ester of amino acid selected from the group consisting of glycine, alanine, leucine, isoleucine, tyrosine, cystine, glutaminic acid, cysteine, homocysteine, glutathione, methionine and ethi0-' ethyl ether and petroleum ether, at a temperature between,

30 and 130 C. and recovering the reaction product from the reaction mixture in solid form.

6. The process of claim 5 in which the ratio of the endiol compound and the second compound reacted is from 2:1 to 1:2.

7. The process of claim 5 inwhich thereaction is carried out in a dry nitrogen atmosphere.

8. A process for the preparation of an ester of cysteine with ascorbic acid which comprises heating under exclusion of oxygen sodium aseorbate with cysteine acid chloride hydrochloride in absolute alcohol at a temperature between 35 and C. and recovering the reaction product from the reaction mixture in solid form.

9. The process of claim 1 in which the ratio of the endiol compound and the second compound reacted is from 2:1 to 1:2.

10. The process of claim 1 in which the reaction is carried out in a dry nitrogen atmosphere.

References Cited in the file of this patent UNITED STATES PATENTS 2,134,246 Elger Oct. 25, 1938 2,350,435 Wells June 6, 1944 2,419,230 Ruskin Apr. 22, 1947 2,539,483 Ruskin Jan. 30, 1951 2,585,580 Opplt Feb. 12, 1952 (Other references on following page) 7 FOREIGN PATENTS Great Britain Ju1y 11, 1956 OTHER REFERENCES Bersin et aL: Hoppe Seylers Zeit. fiir Physiol Chemie,

volume 235, pagesl2-18 (1935). Abderhalden: Fermentforschung, volume 15, page's' page 100 (1948) Q Meyer-Dfiring: Nat ure,- vo1. 174, fp. 555-556 (Sept;

Runti: Chemical A1astr acts, v01, 49, p. 142731 1955 

1. A PROCESS FOR THE PREPARATION OF AN ESTER OF AN AMINO ACID SELECTED FROM THE GROUP CONSISTING OF GLYCINE, ALANINE, LEUCINE, ISOLEUCINE, TYROSINE, CYSTINE, GLUTAMINIC ACID, CYSTEINE, HOMOCYSTEINE, GLUTHTHIONE, METHIONINE AND ETHIONINE WITH ASCORBIC ACID WHICH COMPRISES HEATING UNDER EXCLUSION OF OXYGEN AN ENDIOL COMPOUND SELECTED FROM THE GROUP CONSISTING OF ASCORBIC ACID, ITS ALKALI METAL SALTS AND ITS ALKALINE EARTH METAL SALTS WITH A COMPOUND SELECTED FROM THE GROUP CONSISTING OF GLYCINE, ALANINE, LEUCINE, ISOLEUCINE, TYROSINE, CYSTINE, GLUTAMINIC ACID, CYSTEINE, HOMOCYSTEINE, GLUTHATHIONE, METHIONINE, ETHIONINE AND THEIR HYDROCLORIDES IN A WATERFREE AND INDIFFERENT LIQUID MEDIUM SELECTED FROM THE GROUP CONSISTING OF ABSOLUTE ALCOHOL, ACETONE, ETHYL ETHER AND PETROLEUM ETHER AT A TEMPERATURE BETWEEN 30 AND 130*C. IN THE PRESENCE OF A CATALYST SELECTED FROM THE GROUP CONSISTING OF HYDROCHLORIC ACID, THIONYL CHLORINE AND BORON TRIFLUORIDE AND RECOVERING THE REACTION PRODUCT FROM THE REACTION MIXTURE IN SOLID FORM. 